Effect of rare earth on the microstructure and mechanical properties of as-cast Cu-30Ni alloy

Cu-30Ni-xRE （x = 0-0.213） alloys were prepared by a metal mould casting method. The effect of RE on the microstructure and mechanical properties of the alloys was investigated using optical microscope, scanning electronic microscope with energy-dispersive spectrometer, X-ray diffraction, and mechanical test. The results show that RE has obvious effect on refining dendrite structure and grain size, as well as on purifying the melting of Cu-30Ni alloy. With the increase of RE content, the ultimate tensile strength, yield strength, and elongation increase at first and then decrease after adding RE more than 0.095 wt.%. Cu-30Ni-0.095RE alloy possesses preferable mechanical properties, i.e., the ultimate tensile strength, yield strength, and elongation are 308 MPa, 125 MPa, and 51.2%, respectively. The microstructure and mechanical properties are worsened with increasing RE content more than 0.095 wt.%. The improvement of mechanical properties of Cu-30Ni-0.095RE alloy is attributed to RE refining microstructure and purifying the matrix.

Control of nonmetallic inclusions of non-oriented silicon steel sheets by the rare earth treatment

Based on the industrial production of non-oriented silicon steel, the rare earth （RE） treatment during the Ruhrstahl Heraeus （RH） refining process was studied. The morphology and the size distribution were observed for the steel specimens treated with different RE treatment conditions. Furthermore, the formation and change of the nonmetallic inclusion characteristics of finished steel sheets after the RE treatment were discussed. The results have shown that in the present work,the suitable RE metal additions are 0.6 -0.9 kg/t steel. After the suitable RE treatment,the formation of AIN and MnS inclusions were restrained, and the aggregation, flotation and removal of nonmetallic inclusions were efficiently promoted and the cleanliness of liquid steel was significantly increased. Meanwhile, the total oxygen concentration reached the minimum value and thle desulfurization efficiency was optimal ,and the type of main inclusions was approximately spherical or elliptical spherical RE radicle inclusions whose size was relatively large.

Research and Development of Rare Earth Advanced Materials in China

China is rich in resources of rare earths(REs). Based on tremendous work, China has made great achievements in research and development of REs since 1980s, and the production of RE has won the leading position in the world. The application of RE elements in advanced materials have progressed significantly during the past years. The wide range of rare earth application in China has been reviewed and discussed in this paper, including the development of advanced RE materials (RE-Al alloys, rare earth nonferrous metal alloys, rare earth luminescent materials, rare earth hydrogen storage materials, rare earth permanent magnet and rare earth compounds used in agriculture, i.e., rare earth micronutrient fertilizer etc.) End the research of new RE materials (high T-c rare earth superconductor, rare earth electronic and photonic materials, rare earth ceramics and rare earth precious metal alloys). Finally, the further development works to be required are as follow: (1) to enhance the applied fundamental research, study the intrinsic properties of rare earth elements and develop less well known uses; (2) to undertake the applied research of median and heavy rare earth and find a way out of the unbalance of RE resources in the various applications; (3) to strengthen the applied research of RE element's in energy field, solving the energy-related, energy-saved and environmental problems.

Flotation Separation on Rare Earth Minerals and Gangues

The flotation process of native rare earth minerals such as bastnasite, monazite, mixed minerals of bastnasite and monazite, using the new effective collector Dh was studied, respectively, and the flotation properties were described. The good qualities of the new collector Dh were revealed through comparing with other collector of rare earth minerals. The test results of different ore samples showed that at moderate pulp pH (8.5～9.5), rare earth minerals could be effectively separated from barium, calcium and silicon bearing intergrowth minerals (barite, calcite and silicate minerals) and high quality rare earth concentrates could be obtained successfully by the new collector Dh, acid silica gel, turpentine and reagents fitting together rationally. In order to determine optimum technical conditions, the effect of pulp pH, pulp temperature, pulp density and the effect of dosage of reagents (Dh and acid silica gel) on the flotation were investigated in the test. Simultaneously, the mechanism of the flotation of rare earth minerals from intergrowth minerals was explored. The infrared spectra for Dh and rare earth cation by analysis in theory showed that Dh formed chelate complex with rare earth cation and were adsorbed on the surfaces of rare earth minerals. The mechanism of the intergrowth minerals depressed by acid silica gel can be explained as gummy colloid hydrolyzed from acid silica gel which were selectively absorbed on the gangue minerals, making them hydrophilic and depressed, with pulp pH value of alkalescent.

Influence of Doping Rare Earth on Performance of Lithium Manganese Oxide Spinels as Cathode Materials for Lithium-Ion Batteries

Some rare earth doping spinel LiMn_(2-x)RE_xO_4 (RE=La, Ce, Nd) cathode materials for lithium ion batteries were synthesized by the solid-state reaction method. The structure characteristics of these produced samples were investigated by XRD, SEM, and particle size distribution analysis. According to the microstructure and charge-discharge testing, the effect of doping rare earth on stabilizing the spinel structure was analyzed. Through a series of doping experiments, it is shown that when the doping content x within the range of 0.01～0.02 the cycle performance of the materials is greatly improved. The discharge capacity of the sample LiMn_(1.98)La_(0.02)O_4, LiMn_(1.98)Ce_(0.02)O_4 and LiMn_(1.98)Nd_(0.02)O_4 remain 119.1, 114.2 and 117.5 mAh·g^(-1) after 50 cycles.

HEAT TREATMENT STRENGTHENING EFFECTS OF RARE EARTHS ON Mg-9Al ALLOY

Mg-9Al-xRE magnesium alloys were studied, where, x is 0, 0.4. 0.8. 1.2 and 1.6% (in weight percent, wt%), respectively. Influence of rare earths (RE) on micro structure. and strength in both T4 (solute heat treatment) and T6 (solute heat treatment and artificial ageing treatment) were investigated. Strength of specimen was tested at ambient temperature. The micro structure was analyzed by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction analysis. RE additions improved T4 tensile strength of the treated alloys. Small addition (0.4wt%) of RE greatly improved the strength of ageing treated (T6) Mg-9Al alloy, but further additions caused decreasing.

RE-Si-Al-O玻璃相对高熵稀土双硅酸盐微结构及耐CMAS腐蚀性能的影响

环境障涂层是高功重比航空发动机的关键技术,其目的是阻挡燃气及环境腐蚀介质的侵蚀,为陶瓷基复合材料热端部件提供有效保护。目前,高熵稀土双硅酸盐((xRE_(1/x))_(2)Si_(2)O_(7))是最具潜力的新一代环境障涂层材料。为了进一步提升高熵稀土双硅酸盐的耐高温(1500℃)CMAS(CaO-MgO-Al_(2)O_(3)-SiO_(2))腐蚀能力,本工作设计制备了一种新型高熵(Y_(0.25)Yb_(0.25)Er_(0.25)Tm_(0.25))_(2)Si_(2)O_(7)/RE-Si-Al-O(RE=Yb、Y、La)复相陶瓷。结果表明,在复相陶瓷中,RE-Si-Al-O玻璃相不仅能够包裹陶瓷晶粒,而且能够促进稀土双硅酸盐晶粒长大,减少晶界数量,使CMAS熔体的渗入通道数量减少。同时,随着RE-Si-Al-O玻璃相中稀土离子半径增大,玻璃相更易与CMAS熔盐中的Ca^(2+)离子反应,生成磷灰石相,降低CMAS熔体的活性,抑制高温CMAS熔盐对高熵稀土双硅酸盐晶粒的侵蚀,从而提高高熵稀土双硅酸盐的耐高温CMAS腐蚀能力。在1500℃腐蚀48 h后,(Y_(0.25)Yb_(0.25)Er_(0.25)Tm_(0.25))_(2)Si_(2)O_(7)/La-Si-Al-O复相陶瓷表面仍残留CMAS熔盐层,表明该复相陶瓷具有良好的耐高温CMAS腐蚀能力。该复相陶瓷的微结构设计为增强环境障涂层材料在高温CMAS环境下的长期应用提供了一种新的思路。

A novel process of extraction and separation of RE and Mn from Panxi rare earth mud

A novel process to extract and separate rare earth (RE) and manganese (Mn) from Panxi rare earth mud was developed. The process involves roasting the mud at 480?℃ with NH 4Cl as chlorinating agent, and leaching the calcine with hot water to obtain a rare earth chloride solution. After the solution was further purified, HD(DIBM)P (P 507 ) was applied as extractant to separate RE and Mn. By seven stages of fractional extraction, the RECl 3 and MnCl 2 solutions with 99.8% purity were obtained. Finally, the purified RECl 3 and MnCl 2 solution were precipitated by NH 4HCO 3 to obtain a crystal RE 2(CO 3) 3 and MnCO 3 products respectively.

Kinetics of Formation of Large-Dimension Rare Earth Inclusion in Steels

The elemental distribution within the large-dimension rare earth inclusion in steels was studied through analysis on plane distribution of elements by EPMA (Electron Probe Microanalyzer). The kinetics and mechanism of formation of RE inclusion were discussed, taking 5CrNiMo steel with the addition of RE and other microalloying elements as example. RE inclusions nucleate on oxides and sulphides with high melting point and grow up separately, then integrated by relatively high surface activity, which is a particular characteristic of RE elements, in liquid phase and during the course of solidification. Finally, the fine and dispersed RE inclusions merge and grow into a large-dimension one.

Ab initio calculation of electronic structures and 4f-5d transitions of some rare earth ions doped in crystal YPO_4

The ab initio self-consistent DV-Xa （discrete variational Xa） method was used in its relativistic and spin-polarized model to investigate the ground-state electronic structttres of the crystal YPO4 and YPO4：RE^3＋ （RE=Ce, Pr and Sm） and f-d transition energies of the lattice. The calculation was performed on the clusters Y5P10O32 and REY4P10O32 embedded in a microcrystal containing about 1500 ions, respectively. The ground-state calculation provided the locations of the 4f and 5d crystal-field one-electron levels of RE^3＋ relative to the valence and conduction bands of host, the curve of total and the partial density of states, and the corresponding occupation numbers, etc. Especially, the transition-state calculation was performed to obtain the 4f→5d transition energies of RE^3＋ in comparison to the experimental observations. The lattice relaxation caused by the dopant ion RE3＋ was discussed based on the total energy calculation and the transition-state calculation of the f-d transition energies.

Effects of La-Rich Rare Earth Alloys on Structure and Mechanical Properties of ZL101A Alloy

The effects of La rich rare earth alloys on structure and mechanical properties of ZL101A alloy in as cast, heat treated and remelted states were investigated. The appropriate quantity of the addition of RE alloys and the reasonable heat treatment parameters for integral casting wheel made by low pressure die casting have been suggested.

Effects of Rare Earths and Al on Structure and Performance of High Chromium Cast Iron Containing Wolfram

Effects of RE and Al on the structure, impact toughness, hardness, and wear resistance of high chromium cast iron containing wolfram were investigated. The results show that without modification the volume fraction of austenite is high and the carbide appears to be thick lath and the grain size is relatively large; proper modification using RE combined with Al can reduce volume fraction of residual austenite in the as-cast structure obviously, refine grain size of primary austenite notably, and make the morphology of carbide changing from thick lath to thin lath, rosette, and feather-like modification can also increase hardness, wear resistance and impact toughness of cast iron.

Characteristic of Rare EarthDistribution in Biologic Chains of RE-Rich Back-ground Regions

REE contents of water and vegetables, from two typical RE-rich background regionsand normal region in Gainan,Jiangxi Province, China, indicatethat REE contents are markedlydifferent in water and vegetables.There are average 0.03 mg·L-1and 0. 11 mg·L-1 REE in water ofA and B regions. As REE contentsof vegetables for A region are different from B region, it suggeststhat there are a lot of factors controlling REE distribution betweenvegetables. Comparing with thenormal region, soluble RE contentsin water of the RE-rich backgroundregions are factors of 68 and 18than that of the normal region.REE contents of the most plantsand crops in A and B regions arehigher than that in the normal region. It is clear that REE are theindispensable elements of plantsduring their growing period. Asthere are unusually higher REEcontents of some plants in A and Bthan in the normal regions, it isconsidered to result from absorbingREE passively during the period ofplants and crops growing up.

Grey Interrelation Analysis for the Use of Rare Earths and the Elements in Soil in Growing Cotton

The method of grey interrelation analysis is adopted for the analysis of the relationship between the amount of rare earths applied and the factors of the soil in increasing cotton production in Kazuo County, Liaoning Province. The results show that there is an intimate relation between the use of the RE and the elements in the soil. The pH value, total K, and total P are the main factors influencing the relation, and the total N, hydrolytable N, organic matter, K2O and P2O5 are the secondary factors. This provides a scientific basis for the use of the RE.

Comparative Crystal Chemistry of Rare Earth Minerals

Polyhedral analysis is used to study the geometrical limits of the crystal structure on isomorphic substitution of rare earths.The rare earth sites in the structure may be distinguished into six groups on the basis of mean ionic radii of the substituting cations in each rare earth site:Y,Y+Ca,REE,REE+Ca,Ce+Ca,Ce.The calcula- tion of volumes of 70 rare earth polyhedra indicates that the polyhedral volumes of the heavy rare earth are in a range of 13×10^(-3)～28×10^(-3) nm^3,the volumes of light rare earth polyhedra are in 20×10^(-3)～40×10^(-3) nm^3, and the polyhedral sizes suitable to isomorphic substitution of all REE are about 21×10^(-3)～29×10^(-3) nm^3.The size of REE polyhedra depends on mean ionic radii in REE sites,coordination number and linkage of polyhedra. In structures where exist two kinds of polyhedra,with the change of composition in REE site,both REE polyhedron and anion group polyhedron tend to be more distorted,leading to the change of structural symmetry. The contrary distortion tendencies of both polyhedra favours the stability of the structure.The phenomena may be interpreted by the potential energy distribution or the potential energy compensating mechanism of the crystal.

RE对ZA43合金组织、力学性能及抗磨性的影响

通过RE对ZA43合金进行变质处理,研究了该合金的显微组织、力学性能及抗磨性能。结果表明,在ZA43合金中加入适量RE,能有效地阻止树枝状晶长大,优化组织结构,细化晶粒,使合金的抗拉强度提高20%、硬度提高10%,抗磨性能也大幅度改善。这为进一步改善该合金的力学性能及抗磨性能提供了一条有效途径,从而使锌合金代替铜合金成为可能和现实。

稀土在Al-Ti-B-RE中间合金中的作用

采用氟盐法制备了AlTiBRE中间合金,并对其进行了细化效果实验,利用扫描电镜研究了AlTiBRE中间合金的微观组织特征。研究结果表明加入稀土对TiAl3晶粒的大小、形貌及分布有显著影响;稀土增大了铝熔体与TiB2之间的润湿角,使TiB2不易聚集和沉淀,增强了中间合金的细化性能;稀土易聚集在晶界和相界面,减少晶核与液体间的接触面积,增大形核率,对TiAl3合金晶粒的细化效果明显。

稀土氧化物Ce_2O_3制备Al-Ti-C-RE的热力学分析

采用SEM、EDS和DSC等方法研究稀土氧化物对采用氟盐法制备Al-Ti-C-RE的热力学影响。结果表明:Al与K2TiF6发生铝热放热反应生成TiA13及部分游离态[Ti],在铝热反应的作用下,稀土氧化物Ce2O3与C发生碳热反应,生成大量的CeC2,该相与游离态[Ti]易反应生成TiC和原子态[Ce],反应生成的[Ce]为表面活性元素,吸附在TiA13相上形成Al2Ti20Ce。DSC分析结果表明,添加稀土氧化物Ce2O3可在1 120℃左右自发产生碳热反应。因此,在铝热反应的基础上,利用稀土氧化物与石墨粉之间的碳热反应,不仅可以降低制备Al-Ti-C-RE细化剂的反应温度,同时还可提高C与铝熔体的润湿性,促进TiC粒子的生成。

粉末法RE-B共渗机理

研究了粉末法 RE-B 共渗活性原子的产生、吸收和共渗层形成的机理,以及稀土元素在渗层中的迁移过程。结果表明,活性稀土元素原子可通过热还原产生;稀土元素促进了活性硼原子的产生、吸附与吸收;稀土元素原子的扩散和钢中杂质元素 Si、S、P 等以及渗层中的各种晶体缺陷有着密切的联系。

电积铜用新型Pb-Ca-Sn-Re合金阳极的制备及其性能

为了获得机械强度高、电化学性能优良的铜电积铅基合金阳极材料,采用合金重熔法制备了Pb-1.00%Ca、Pb-0.06%Ca-0.60%Sn、Pb-0.06%Ca-0.60%Sn-0.10%Re合金;通过金相分析、硬度测试研究了稀土元素对合金组织及力学性能的影响,采用扫描电镜(SEM),X射线衍射(XRD)、阳极极化、Tafel曲线、循环伏安(CV)曲线对3种合金阳极的耐蚀性及电催化活性进行了研究。结果表明:稀土元素可以抑制导电性较差的PbSO4的生成,促进导电性好的PbO2的生成,从而降低阳极电位,提高电催化活性;同时膜层变得更加致密,其中Pb-0.06%Ca-0.60%Sn-0.10%Re合金的电催化活性和耐腐蚀性能最好。